Surface modification of inorganic nanoparticles for development of organic–inorganic nanocomposites—A review

Emulsions stabilized with solid nanoparticles: Pickering emulsions

Nanomaterials (NMs) are gaining significance in technological applications due to their tunable chemical, physical, and mechanical properties and enhanced performance when compared with their bulkier counterparts. This review presents a summary of the general types of NMs and provides an overview of the various synthesis methods of nanoparticles (NPs) and their functionalization via covalent or noncovalent interactions using different methods. It highlights the techniques used for the characterization of NPs and discusses their physical and chemical properties. Due to their unique properties, NMs have several applications and have become part of our daily lives. As a result, nanotoxicity research is gaining attention since some NPs are not easily degraded by the environment. Thus, this review also highlights research efforts into the fate, behavior, and toxicity of different classes of NMs in the environment.

Nanomaterials: Classification, properties, and environmental toxicities

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Current Trends in Pickering Emulsions: Particle Morphology and Applications

The preparation of nanoparticles in a soap-free system is highly attractive, as surfactants may influence and deteriorate subsequent applications. Thereby, the assembly of solid particles on droplets/particles is well known as Pickering-type stabilization. The resulting hybrid nanocomposites offer in general a rough surface and are highly intriguing for potential drug delivery systems, coating applications, and so forth. This review highlights developments in production and application of Pickering-type nanoparticles synthesized via heterophase polymerization techniques in emulsion, miniemulsion, dispersion, and suspension. We will focus our discussion on systems, wherein stabilization of the final nanometer-sized hybrids is exclusively accomplished via particle stabilizers. In case surfactants are used during preparation, they only serve as pre-treating agents to modify the surface properties of the particle stabilizer, and not being employed for the purpose of droplet/particle stabilization.

Pickering-type stabilized nanoparticles by heterophase polymerization

Facile photocatalytic emulsion polymerization was developed to fabricate polystyrene (PS) microspheres using a transparent anatase titania hydrosol both as a photocatalyst and stabilizer. Under the appropriate conditions, PS microspheres with a well-defined particle size distribution can be easily produced from 100 to 830 nm. The effects of cross-linking agent ethylene glycol dimethacrylate (EGDMA) and coupling agent acrylic acid (AA) on the particle size and the size distribution of PS microspheres were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and other characterization means. It is proven that EGDMA and AA play importance roles in the morphology of microspheres. In addition, AA bonds a large number of titania nanoparticles on the surface of PS microspheres because its carboxyl group forms inorganic armored polymer microspheres. This interfacial interaction between titania nanoparticles and PS chains causes the elevated glass-transition temperature of microspheres.

Fabrication of polymer microspheres using titania as a photocatalyst and pickering stabilizer.

PMMA-silica hybrid thin films with enhanced thermal properties prepared via a non-hydrolytic sol-gel process

Polystyrene (PS) nanocomposite particles with high titania content are prepared by Pickering emulsion polymerization. A self-made titania hydrosol modi- fied by an anionic monomer sodium styrene sulfonate (NaSS) is used as a stabilizer and photocatalyst. The stability of the emulsion system is greatly improved by the electrostatic interaction between negatively charged NaSS and positively charged titania nanoparticles. The nanocomposite spheres with the diameter of around 120 nm are highly charged, indicating titania-rich surfaces of latex particles. It is also proven by the field-emission transmission electron microscope and field-emission scanning electron microscope images. The well-defined core-shell structure of the obtained PS/titania composite particles is confirmed by the formation of fragile hollow titania nanospheres after thermogravimetric analysis tests. V C 2009 Wiley

Effect of an anionic monomer on the pickering emulsion polymerization stabilized by titania hydrosol

Two kinds of PS microspheres with different structures are prepared in one reaction system via Pickering emulsion polymerization. As the stabilizer, titania nanoparticles are modified by oleic acid or sodium oleate and then investigated using aqueous electrophoresis measurements, DLS and oil/water partitioning experiments. The morphology of the resulting polymer microspheres is characterized using TEM and FE-SEM. It is proven that the surface structure of the titania nanoparticles determines the polymerization routes it adopts and affects the morphology of the final polymer microspheres.

Xiaomei Song

Papers

Fabrication of polymer microspheres using titania as a photocatalyst and pickering stabilizer.

PMMA-silica hybrid thin films with enhanced thermal properties prepared via a non-hydrolytic sol-gel process

Effect of an anionic monomer on the pickering emulsion polymerization stabilized by titania hydrosol

Fabrication of Two Kinds of Polymer Microspheres Stabilized by Modified Titania during Pickering Emulsion Polymerization

Surface initiated graft polymerization from carbon-doped TiO2 nanoparticles under sunlight illumination